Scientists from ExxonMobil, the Georgia Institute of Technology and Imperial College of London have published in the journal Science joint research on potential breakthroughs in a new membrane technology that could reduce emissions and energy intensity associated with refining crude oil. Laboratory tests indicate the patent-pending membrane could be used to replace some heat-intensive distillation at refineries in the years ahead.

The fractionation of crude-oil mixtures through distillation is a large-scale, energy-intensive process. Membrane materials can avoid phase changes in such mixtures and thereby reduce the energy intensity of these thermal separations. With this application in mind, we created spirocyclic polymers with N-aryl bonds that demonstrated noninterconnected microporosity in the absence of ladder linkages. The resulting glassy polymer membranes demonstrated nonthermal membrane fractionation of light crude oil through a combination of class- and size-based “sorting” of molecules. We observed an enrichment of molecules lighter than 170 daltons corresponding to a carbon number of 12 or a boiling point less than 200 °C in the permeate. Such scalable, selective membranes offer potential for the hybridization of energy-efficient technology with conventional processes such as distillation.

—Thompson et al.

The research successfully demonstrated that naphtha and kerosene—the primary components of gasoline and jet fuel—can be separated from light crude oil using pressure instead of heat, reducing emissions and energy consumption significantly compared to traditional, heat-based distillation methods.

By substituting the low-energy membranes for certain steps in the refining process, the new technology might one day contribute to a hybrid refining system that could help reduce carbon emissions and energy consumption significantly compared to traditional refining processes.

A molecular model of the polymer membrane, with the pores shown in blue. Imperial College London.

Inspired by reverse osmosis technology that has reduced energy intensity tenfold for water purification, we decided to look into ways to use new materials for liquids separation, which if brought to industrial scale, could significantly reduce associated greenhouse gas emissions. This is one of many new materials ExxonMobil is researching to reduce energy intensity and CO₂ in our operations.

—Vijay Swarup, vice president of research and development at ExxonMobil Research and Engineering Company

Since 2014, the team of scientists has worked to identify advanced membranes to separate light shale crude oil using significantly less energy than used in typical refining processes.

Membrane technology is already widely used in applications such as seawater desalination, but the complexity of petroleum refining has until now limited the use of membranes. To overcome this challenge, the research team applied a new polymer to a surface to create membranes able to separate the complex hydrocarbon mixtures that make up crude oil through the application of pressure rather than heat.

The team balanced a variety of factors to create the right combination of solubility, which enables membranes to be formed by simple and scalable processing, and structural rigidity, which allows some small molecules to pass through more easily than others.

The researchers found that the materials needed a small amount of structural flexibility to improve size discrimination, as well as the ability to be slightly ‘sticky’ toward certain types of molecules that are found abundantly in crude oil.

The polymers were designed and tested at Georgia Tech, then converted to 200-nanometer-thick films and incorporated into membrane modules at Imperial. In the gasoline and jet fuel range, the membranes developed by the team are twice as effective as the most selective commercial membranes in use today.

This membrane technology was developed by a diverse team of scientists and engineers using a ‘multi-scale’ approach that ranges from the molecular-scale to realistic membrane devices.

—Ryan Lively, the John H. Woody faculty fellow and associate professor in Georgia Tech’s School of Chemical & Biomolecular Engineering

It’s rare that chemists have the chance to participate in both inventing new molecules and applying them to solve real-world problems. In this case, it really took a whole village of differing expertise to bring to fruition a new approach for separating the components of crude oil using much less energy than before.

—M.G. Finn, Chair of the School of Chemistry & Biochemistry at Georgia Tech and a joint lead of the study

Additional research and development will be needed to progress this technology to industrial scale.

We have the foundational experience of bringing organic solvent nanofiltration, a membrane technology becoming widely used in pharmaceuticals and chemicals industries, to market. We worked extensively with ExxonMobil and Georgia Tech to demonstrate the potential scalability of this technology.

—Andrew Livingston, professor of chemical engineering at Imperial

Since 2000, ExxonMobil has invested approximately $10 billion in projects to research, develop and deploy lower-emission energy solutions. The company also continues to expand collaborative efforts with more than 80 universities, five energy centers and multiple private sector partners around the world to explore next-generation energy technologies.

The researchers on the technology as written in Science include Neel Rangnekar, J.R. Johnson, Scott Hoy and Benjamin McCool from ExxonMobil; Kirstie Thompson, Ronita Mathias, Ryan Lively and M.G. Finn from Georgia Institute of Technology; Daeok Kim, Jihoon Kim, Irene Bechis, Andrew Tarzia and Kim Jelfs from Imperial College London; and Andrew Livingston, concurrently with Imperial and Queen Mary University of London.

Resources

• Kirstie A. Thompson, Ronita Mathias, Daeok Kim, Jihoon Kim, Neel Rangnekar, J. R. Johnson, Scott J. Hoy, Irene Bechis, Andrew Tarzia, Kim E. Jelfs, Benjamin A. Mccool, Andrew G. Livingston, Ryan P. Lively, M. G. Finn (2020) “N-Aryl–linked spirocyclic polymers for membrane separations of complex hydrocarbon mixtures” Science doi: 10.1126/science.aba9806